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I've got a scanned signature that I'm trying to clean up. I was able to use levels to remove some of the grain surrounding the handwriting, but I cannot figure out how to remove the grain from the actual signature. I'm just looking to have all the minute speckles to be joined together as one black seamless line. I feel like this would be pretty easy to do: I have the signature in a separate layer, but going through the filters didn't get me the result I'm going for. Here's part of the image I'm working with to give you an idea:

enter image description here

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  • Copy layer
  • Set blend mode of copy to Multiply
  • Filter > Blur > Gaussian Blur set this to 1 pixel.
  • Duplicate blur/multiply layer 3 or 4 more times.

enter image description here

  • Choose Merge Visible from the Layer Panels menu
  • Filter > Other > Maximum - set this to 1 pixel.

enter image description here

  • Image > Adjustments > Levels to tweak things a bit more....

enter image description here

You will probably need to go in with a small brush and draw the hole in the "dot" of the lowercase i. (which I did not do)

  • 3
    Too bad Photoshop doesn't have a flourier transform. – joojaa Oct 13 '14 at 18:57
  • @joojaa Doesn't PS use an FFT for each convolution? Otherwise, it would choke on large images. – Navin Oct 13 '14 at 20:56
  • @Navin I doubt it does. – joojaa Oct 13 '14 at 21:04
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    @Navin to add, makers of adobe isnt exactly known for its superior signal prosessing functionality. I mean they dont even offer many of the standard scaling filters, and untill recently they weere pretty awfull in this domain. Adobe isnt standard for superior code its standard because they dominated the print business. – joojaa Oct 13 '14 at 21:23
  • @joojaa "fourier* transform"? – SaturnsEye Oct 14 '14 at 8:16
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Here's what I managed using GIMP; I believe all the steps should be possible in Photoshop too:

  1. (optional) Convert image to pure black and white, using Color > Threshold with the threshold at 128.

  2. Apply a very small amount of Gaussian blur; I got best results with a radius of 0.6 px, but you may wish to play with different radii.

  3. Apply Color > Threshold again, this time choosing a higher threshold, so that any white pixels surrounded by enough black pixels in the original picture get filled in.

Result:
Image

8

To me Photoshop + Illustrator combination works best:

Photoshop:

  1. Go to: Image > Image Size...> and resize it to 200%. The resize scale depends on the image and is to make sure that the shape blur used in the next step is not too big.
  2. Go to: Filter > Blur > Shape Blur... >. Use minimum blur radius (5px), select Shapes object group from a side menu and select a filled circle shape and blur it:

enter image description here

  1. Go to: Image > Adjustments > Threshold... > and select the value that gives optimum smoothness and thickness. As a result you'll have a sharp-edged graphics, without shadows. If we resize the artwork back to original size we would have: enter image description here

Now, if we want the edges even smoother:

Illustrator:

  1. Import the still resized artwork into Illustrator.
  2. Go to Object > Image Trace > Make. These default settings worked well for me:

enter image description here

  1. Go to: File > Save for Web... > and export to match the original size / format.

The result is:

enter image description here

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  • Select the white background. Select > Color Range.
  • Invert the selection. Select > Inverse.
  • Grow the selection by 1 pixel. Select > Modify > Expand.
  • Shrink the selection by 1 pixel. Select > Modify > Contract.

Take the result, push into Illustrator or Inkscape, and convert to a path:

enter image description here

  • Sad... your result is nice but I simply can't reproduce it because your explanation is too high level... – Maxime Oct 11 '16 at 18:24

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